The two oscillator circuits under are suitable for employing crystal oscillators in series or parallel method: Large-repetition-amount and higher-electricity picosecond regenerative amplifier based on an individual bulk Nd:GdVO4 crystal A timing reference incorporating only one-crystal-silicon micromechanical resonator with a quality element of much larger than one million along with a https://www.hxcrystals.com/seokeywords/bulk-crystal-oscillator.html